Short story: I want to build a lightweight, stiff, and fast gantry for my existing machine. My goal is 200 IPM carves that don't show oscillation marks due to machine flex and/or backlash.


More details: I have a 25 year old 4' x 8' Vytek Rebel router that's painfully slow on 3D carves. Because the gantry alone is around 400lbs, I get oscillation marks in the carve if I have the speed up much past 60-70 IPM. This is due to flex in the Z drive carriage, a 45lb spindle, and 25 years of wear on the machine. So, after seeing a lightweight, and fast machine at the Vectric group meeting in Denver last week, I was inspired to build a light, stiff, and fast gantry for my bulldog of a base & bed.


The gantry (X-axis) is essentially a rack & pinion, which drive from both sides of the gantry. The rack is a 75mm wide steel reinforced 5 TPI precision timing/power-transmission belt. The pinion is a matching toothed pully driven by a stepper with a drive shaft to the other side of the gantry. There's no measurable backlash in the gantry, and it runs within .001" - ,002" from where it's supposed to be anywhere on the bed. The gantry runs on 3/4" round linear rails with 2 linear bearings per side.

The Y and Z axes are ball screw. I have about .001" backlash in the Y axis, The Z axis is much worse at .008", which is accommodated for in Mach3.

I'd like to use my current linear rails. They're strong, and already tuned to the base. The rest I figure will be new. I'm thinking of a dual motor rack & pinion drive for the gantry, and single rack & pinion for Y, and Z.

Is my 45lb 5 HP Perske spindle too heavy to use to get to my desired non-floppy 200IPM?

This seams possible, but having not built a machine, I'm not sure where to start. I need help with parts selection and design.

Thanks for reading, and where should I start?

Chris